Polish the triangle and circle

[amanda-phet]

The slight overlap make the circle have a funny shape, so we should probably do something here like make the circle radius slightly smaller or move the triangles to the sides slightly.

@chrisklus is going to layer the circle on top of the triangle, for now, so we don't see the pointy part overlapping.

[chrisklus]

I discovered that I created this overlap intentionally, likely to avoid too much of the tick marks from peeking through behind the tip of the triangle:

So I proceeded with layering the circle on top of the triangles and actually moving the triangles another half a pixel closer to the circles to cover the thicker tick marks behind the triangle:

I think this is looking good and ready to close. @amanda-phet feel free to reopen if you disagree.